MANCHESTER - Authorities continue to investigate the suspicious deaths of two people whose bodies were discovered in a burning home on Monday and are asking the public for help in locating a "person of interest" - the homeowners' son.

Police have yet to find Matthew Dion, 38, who lived at the 210 Mooresville Road home with his parents, Bob and Connie Dion. Investigators released additional photographs of Dion who they said is believed to be operating a white 2009 Nissan Altima with New Hampshire registration 341-0587.

Autopsies were scheduled for Wednesday morning on the bodies, after which authorities are expected to release their identities.

Relatives of Bob and Connie Dion believe they are the victims.

Police and fire investigators remained on the scene Wednesday, where yellow police tape still cordons off the split level home. A red trailer from the state Fire Marshal's Office and the Manchester Police Department's Critical Incident Response Team truck both were parked on site.

Firefighters were inside the heavily damaged home and two were seen in the rear going through rubble.

Anyone with information regarding the whereabouts of Matthew Dion or the described vehicle is urged to call 911, or Manchester police at (603) 668-8711.

"I don't think we have any solid leads at this point (into his whereabouts)," Janice Rundles, a homicide prosecutor with the New Hampshire Attorney General's Office, said Tuesday night.

Jim Normand, a Manchester lawyer hired to represent a nephew of the Dions in a likely Probate Court case, said his client Roger Mitchell has met with investigators. Normand said the family is fairly confident the bodies, found together in the ground floor of the split level home, are those of Bob and Connie Dion.

Rundles said police agencies in the state have been notified about Matthew Dion and a missing family car, a white, 2009 Nissan Altima with a New Hampshire registration 341-0587. Dion is described as 5 foot 8 inches and about 200 pounds. He has brown hair and brown eyes.

Authorities know the location of the other family car, and that is part of the investigation, Rundles said.

"The million-dollar question is, 'Where is my cousin?'" said Michael Mitchell. Family members have said that Matthew Dion lived at the house along with Michael Focosi, the teenage son of Dion's fiance.

Gathering evidence

The fire and discovery of the bodies are part of investigations that involve Manchester police and fire officials, the state Fire Marshal's Office and the U.S. Bureau of Alcohol, Tobacco and Firearms.

Throughout the day Tuesday, police and fire officials combed the property and entered and exited the house. Police and fire agencies parked trailers outside the house at 210 Mooresville Road, and used the adjacent parking lot of the Manchester Church of God.

Investigators who entered the split-level house wore face masks. Yellow police crime-scene tape was stretched across the yard. Trucks from several Boston television stations were parked on a nearby lot.

"Obviously, it's a very complicated scene," Rundles said. She said investigators were working to determine both what caused the fire and gather evidence about the deaths, Rundles said.

The fire was called in at 2:37 p.m. Monday by people who said they heard an explosion.

The bodies were discovered after firefighters had all but extinguished the flames. With reports of an explosion, and a visible shift in a portion of the front exterior wall, firefighters had worked to brace the structure before entering it.

District Fire Chief Michael Gamache said an explosion was the result of a flashover or smoke explosion. It knocked the building a foot off the foundation and blew off both the front and rear doors. He said a flashover occurs when a fire reaches a temperature of between 500 and 600 degrees, blowing out windows.

"It was a violent explosion that knocked the house off its foundation," Gamache said.

Family interviewed

Rundles said authorities have interviewed family members, who have been cooperative in the investigation. Family and friends of the Dions have also spoken to reporters.

The retired couple have been described as loving and outgoing. They opened their home to family when they needed a place to stay. Retired and in relatively good health, they pursued their interests — travel, stamp collecting and quilting, friends said.

Family members have said that Bob Dion's stamp collection was significant and valuable, but Rundles would not discuss the collection or whether it was intact.